1. Field of the Invention
The present invention relates to a damper assembly which can attenuate the vibration occurring during washing, and more particularly, to a snubber base which moves up and down in a damper cap of a damper assembly in a washing machine, during which the snubber base makes contact with the damper cap.
2. Discussion of the Related Art
A washing machine, strips off contaminants such as dirt that is stuck on laundry, in general, by means of water circulation formed from the rotational force of a pulsator, and conducts either a washing or rinsing mode by means of pulsatile and rotational circulation of the water in an outside tub. The rotational force is formed by a regular or reverse direction rotating force of a motor. A driving force, is transmitted to the pulsator through a clutch-controlled speed reduction mechanism of clutch to rotate the pulsator. A washing machine also conducts a spin drying mode by means of the centrifugal force produced as the inside tub rotates. In a washing machine that uses water circulation strength or form to wash the laundry, the washing is carried out by stripping contaminants off the laundry with a combination of the mechanical actions of water shearing force, the bending and, stretching of the laundry, the friction exerted by and on the laundry, and chemical action of detergent.
FIG. 1 illustrates a cross sectional view of a conventional washing machine, including an outside tub 2 in a body 1 of the washing machine supported by a plurality of damper assembly 3, an inside tub 4 rotatably mounted in the outside tub for accommodating laundry (not shown), and a pulsator 5 rotatably mounted on a bottom of the inside tub 4 at a center thereof for generating a pulsatile circulation. The pulsator 5 is fixed to a shaft 7 rotated by a motor 6. A and there is a clutch under the shaft can be engaged to selectively rotate either the inside tub 4 or the pulsator 5. The rotational force generated by the motor is transmitted thereto through a timing belt 8. A water supplying device at the top of the body 1 selectively supplies, depending on selection of a water supplying mode of a user, either cold water and hot water simultaneously or cold water or hot water selectively, into the outside tub A detergent box 11 is located at an outlet in the water supplying device for automatic introduction of detergent into the outside tub 2 with the initial water supply when a washing mode is set A drain valve 12 is located at a lower portion of the outside tub for draining waste water after completion of washing.
Accordingly, after opening a door 13 on top of the body 1, and introducing the laundry into the inside tub 4, opened door 13 is closed and a washing mode is set on the control panel. When operating, the washing, rinsing, and dehydrating cycles are conducted in succession in response to control signals from a controller. Upon setting the washing mode in the controller, after the pulsator 5 is rotated to determine a weight of the laundry to determine a quantity of water to be supplied, the determined quantity of water is supplied into the inside tub 4. The detergent in the detergent box 11 is automatically introduced into the inside tub 4 together with the water supply. Upon completion of supply of the water and detergent into the inside tub 4, power is applied to the motor 6, generating a rotating force, to rotate a motor shaft in regular and reverse directions, intermittently. When the rotating force of the motor is transmitted to the clutch 9 through the timing belt 8 wound between the pulleys 14a and 14b, as the motor is driven, the clutch 9 rotates the pulsator 5 fixed to the shaft 7 at a reduced speed, to form a pulsatile circulation in the water in the inside tub 4 to circulate the laundry. Thus, washing of the laundry is made by a pulsatile circulation, friction between the inside tub 4 and the laundry and dissolving effect of the detergent. After proceeding through the aforementioned washing cycle for the laundry for a preset time period, drain valve 12 opens in response to a control signal from the controller drain waste water in the inside tub 4 to outside of the body 1. Upon completion of draining the waste water from the inside tub 4, water is supplied to inside tub 4 by an operation identical to the above operation, and pulsator 5 is operated for a preset number of pulses, to conduct the rinse cycle. While the water is supplied for the rinse cycle, no detergent is present in the detergent box 11. After completion of the rinse cycle, the clutch 9 is changed over from the pulsator 5 to the inside tub 4, to rotate a inside tub 4 without reduction in speed while leaving the pulsator 5 stationary in this manner, the washing machine conducts its spin cycle to remove water from the laundry. When the spin cycle is finished, an alarm indicates that the washing is complete and operation of the washing machine is finished.
In the washing machine, described above while in the washing, rinsing and spinning cycles where is a vibration resulting from the to driving of the motor in each of the modes and also from the circulation of the water and the laundry during washing and rinsing. This vibration causes noises during operation of the washing machine. In order to attenuate the vibration produced during operation of the washing machine, the outside tub 2, which has parts such as motor 6 and clutch 9 mounted thereon as shown in FIG. 1, is suspended from body 1 by means of a plurality of damper assemblies 3. The damper assembly 3 gradually attenuates vibration with spring damping, frictional damping from sliding between solid state bodies and air compression damping.
FIG. 2 schematically illustrates a perspective view showing conventional damper assemblies mounted in a washing machine. FIG. 3 illustrates a cross sectional view of the damper assembly shown in FIG. 2.
The damper assembly 3, mounted between the body 1 and the outside tub 2 for absorbing and attenuating the vibration generated during operation of the washing machine, will be explained with reference to FIGS. 2 and 3.
The damper assembly 3 includes an upper corner 15 at every corner inside of the body 1, an upper pivot 16 coupled to each of the upper corners, a snubber bar 17 having one end supported by the upper pivot and the other end hung from the one end, a plurality of supporting members 18 each formed on an outside circumference of the outside tub 2 at a lower side thereof, a damper which receives the other end of the snubber bar and supported by the supporting member 18 for damping the vibration. The damper 19 includes a guide bar 20a formed at top of a damper cap 20 as a single unit therewith for guiding up and down movements of the damper cap 20 along the snubber bar 17, a snubber base 21 coupled with the snubber bar at a bottom thereof for making up and down movements while making a close contact with an inside circumference of the damper cap, a damping spring 22 accommodated in the damper cap, inserted in the snubber bar and held in place by the snubber base, and a washer 23 inserted to the snubber bar under a bottom of the snubber base for preventing deformation of rubber of the snubber base during operation.
The aforementioned damper assembly 3 gradually attenuates the vibration generated either from the pulsatile circulation caused by centrifugal force of the pulsator 5 rotation and the laundry gathered to one side as the laundry circulate during washing or rinsing mode, or by inclination of the inside tub 4 and the laundry gathered as the inside tub 4 rotates during a dehydrating mode.
For example, if the laundry is gathered to one side at completion of drainage in the dehydrating mode, the inside tub 4, rotated with an inclination at an initial rotation, generates vibration, which is attenuated by the damper 19 between the body 1 and the outside tub 2. That is, the damper cap 20, supported by the supporting member 18 surrounding an outside circumference of the snubber bar 17 passed through and hung from the upper pivot 16 and having a top thereof connected to the outside tub 2, dampens the vibration as it is compressed and expanded in directions as shown by arrows in FIG. 3.
If the body 1 is away from the outside tub 2 due to the inclination of the inside tub 4, the outside tub 2, guided by the guide bar 20a at top of the damper cap 20, moves down along the outside circumference of the snubber bar 17. As the damper cap 20 moves down, the damper cap 20 rubs against an outside circumference of the snubber base 21 which is in close contact with the inside circumference of the damper cap 20 and the air inside of the damper cap 20 is compressed, to attenuate most of the vibration occurring during rotation of the inside tub 4. Moreover, the spring in the damper cap 20 is compressed when the damper cap 20 moves down to dampen the vibration.
If, on the other hand, the body 1 and the outside tub 2 come closer due to the inclination of the inside tub 4, the damper cap 20, guided by the guide bar 20a at top of the damper cap 20, moves up along the outside circumference of the snubber bar 17. As the damper cap 20 moves up, the damper cap 20 makes friction with an outside circumference of the snubber base 21 which is in close contact with the inside circumference of the damper cap 20 and the air inside of the damper cap 20 is expanded, to attenuate most of the vibration occurring during rotation of the inside tub 4. Moreover, the spring in the damper cap 20 is extended when the damper cap 20 moves up to dampen the vibration.
Of these vibration absorbing mechanisms of solid state friction damping (i.e., produced from sliding of the inside circumference of the damper cap 20 in contact with the outside circumference of the snubber base 21, air compression damping produced from compression of the air in the damper cap 20, and spring damping produced from compression and extension of the damping spring 221, the most important component to the damping is the snubber base 21 that moves up and down inside of the damper cap 20 to compress and extend the damping spring 22. This component to damping is important because the damping coming from friction as well as the damping coming from air compression results only if the outside circumference of the snubber base 21 makes close contact with the inside circumference of the damper cap 20. The part that continuously maintains the damping of the damper 19 effective by causing the outside circumference of the snubber base 21, i.e., the sliding surface to make a close contact with the inside circumference of the damper cap 20 is the snubber base spring 24 inserted in the inside circumference of the snubber base 21. The snubber base spring 24 should be adapted to keep a state in which the snubber base spring 24 is fitted in the snubber base 21 and to apply a force to the snubber base 21 continuously to expand the snubber base 21. To do this, as shown in FIG. 4, there is a recess 21 a formed in the inside circumference of the snubber base 21 which is held at the other end of the snubber bar 17 for making up and down movements in the damper cap 20, for the purpose of inserting the snubber base spring 24 therein. Although in most cases, the snubber base 21 is formed of a rubber, it may be formed of a plastic. When the damper 19 has a rubber snubber base, since it is not self lubricative with a great friction, a coat of fluororesin is applied to the outside circumference of the snubber base 21 to reduce the friction, for smoother sliding movements at a contact surface between the damper cap 20 and the snubber base 21. And, there is a steel washer 23 fixed under the bottom of the snubber base 21 which is held at a lower end of the snubber bar 17 for preventing distortion of the snubber base 21 of a comparatively soft material during operation. However, when the damper 19 has a plastic application snubber base 21, though the application of fluororesin coating to the sliding surface(the outside circumference) is not required because the plastic is self lubricative and no washer is required because rigidity of the plastic is greater than the rubber, an appropriate friction between the inside circumference of the damper cap 20 and the outside circumference of the snubber base 21 will not be provided unless a separate elastic body is not inserted in the inside circumference of the snubber base 21. Because injection molding of the recess 21a in the inside circumference of the snubber base 21 for inserting the elastic body, under-cutting the snubber base 21, is not easy to process, the elastic body is not actually provided to the snubber base 21.
Instead either a coil spring 24a as shown in FIG. 5A or a tension spring 24b as shown in FIG. 5B is used as a substitute for the snubber base spring 24 and expand the snubber base 21 so that the snubber base 21 can make close contact with the inside circumference of the damper cap 20. However, as the coil spring 24a has a smaller elastic force that is not enough to cause the outside circumference of the snubber base 21 to make a close contact with the inside circumference of the damper cap 20, the tension spring 24b is used in most of the cases. Both ends of the tension spring are bent inwardly for easy of assembly and preventing tearing of the snubber base 21 of rubber.
However, the aforementioned conventional damper assembly has the following problems.
First, if tension spring 24b is use as the snubber base spring 24, because there is no means for preventing the tension spring 24b from moving in a direction of the arrow shown in FIG. 4 along the recess 21a formed in the inside circumference of the snubber base 21 during the up and down movements of the snubber base 21 inside of the damper cap 20, it is frequently observed that the tension spring 24b comes off out of its position, resulting in degradation of the solid state friction damping coming from the sliding friction because the outside circumference of the snubber base can not make a close contact with the inside circumference of the damper cap 20 during the up and down movements of the snubber base 21. If coil spring 24a is applied as the snubber base spring 24, and the spring does not have enough force to expand the snubber base 21, the space inside of the damper cap 20 will be insufficiently can be hardly sealed and there may insufficient friction at the contact surface between the damper cap 20 and the snubber base 21.
Second, there can be a distortion of the snubber base 21 caused by the temperature rise resulting from the friction between the damper cay 20 and the snubber base 21 during vibrations. The distortion causes the seal to break between the inside circumference of the damper cap 20 and the snubber base 21 of vibration by the friction and sealing is minimal. Furthermore, as the fluroresin applied to the sliding surface 21b wears down the friction caused by the direct contact of the rubber outside circumference of snubber base 21 with the inside surface of the damper cap 20, causes the lower lip of the snubber base 21 to turn inside out. In other words, the strong friction at the direct contact of the rubber, which has a greater friction than the fluororesin, with the inside circumference of the damper cap when the damper cap 20 moves down causes the lip of the snubber base 21 to turn inside out. This inversion of the lip results in the snubber base spring coming out of the recess 21a and causes the aforementioned problem namely, breaking the seal between damper cap 20 and snubber hase 21.
Third, if due to a severe vibration the snubber base 21 comes out of the damper cap 20, through the bottom opening of the damper cap 20 snubber base spring 24 may fall out of the snubber base. The soft rubber of snubber base 21 is expanded by the elastic force of the snubber base spring 24 to a diameter greater than the inside diameter of the damper cap 20. Thus, if snubber base spring 24 hits the bottom of the damper cap 20 at rise of the snubber base 21, the spring may fall out of the snubber base and cause the aforementioned problem.
Fourth, under certain circumstances can extend the lower end of the snubber bar 17, beyond the bottom of the snubber base and hit the steel washer 23 which generates noise or, if the snubber base 21 is plastic, in which case no steel washer is inserted in the snubber base 21 due to the rigidity of plastic, the plastic snubber base may break when the snubber bar hits the snubber base 21 due to the incapability of pushing down of the snubber base 21 during the upward movement of the damper cap 20 coming from degradation of the elastic force of the damping spring 22 after repeated vibration absorption action. This leads to an impact on the bottom of the snubber base 21 when the damper cap 20 moves down again, which causes the lower end of the snubber bar 17 to hit the steel washer or plastic snubber base.